1. Field of the Invention
This invention relates to a marking device used in marking the surfaces of products during molding process.
2. Description of the Prior Art
According to the development of plastic molding technique and new resins, various resin materials are used in molding process. Some resin materials used in molding process generate gas during heating process. The gas generated from the resin materials may cause defects of the molded products.
Gas-exhausting apparatuses are generally used to exhaust the gas generating in the molding processes out of a cavity of a molding device. Japan Patent Publication No. 2002-127145 discloses one example of the gas-exhausting apparatuses. FIG. 12 shows the gas-exhausting apparatuses disclosed in the patent publication.
FIG. 12 shows a cavity (C), an upper molding part (U) defining the upper end of the cavity (C), and a molding device including a lower molding part (L) defining the lower end of the cavity (C). A gas-exhausting apparatus (E) is inserted from the bottom end of the through-hole vertically penetrating the lower molding part (L). The molding device (M) further comprises a supporting plate (S) supporting the bottom surface of the gas-exhausting apparatus (E).
The gas-exhausting apparatus (E) is provided on its upper surface with a plurality of gas-exhausting holes. The gas-exhausting holes leads to a gas-exhausting path (P) formed in the gas-exhausting apparatus (E). The gas-exhausting path (P) communicates with the space formed between the outer peripheral surface of the gas-exhausting apparatus (E) and the inner wall defining the through-hole extending through the lower molding part (L). The gas-exhausting path (P) also communicates with the space formed between the lower molding part (L) and the supporting plate (S). Through such structure, the gas generating in the cavity (C) is exhausted.
The gas-exhausting apparatus (E) disclosed in the above-mentioned Japan Patent Publication No. 2002-127145 further includes a cooling structure (F). The cooling structure (F) produces a cooling effect while containing water therein.
The gas-exhausting apparatus (E) has some shortcomings although it advantageously has a cooling function as well as a gas-exhausting function.
For example, the gas-exhausting apparatus cannot sufficiently exhaust gas from a certain shape of cavity. If the products to be molded have a complicated shape, in particular, in their edges, gas tends to accumulate in the corner of the cavity that defines the edge of the molded products. Since the gas-exhausting apparatus (E) disclosed in the above-mentioned patent publication is comparatively bulky and needs to be supported on its bottom surface by the supporting plate, it is difficult to position the gas-exhausting apparatus in the corner of the cavity with a complicated shape.
Also, most molded products are marked with their manufacturing date, lot numbers, manufacturing line numbers, and the like. Such markings are useful in distribution management and quality management of the molded products but they spoil smoothness of the product surface.
When the gas-exhausting apparatus (E) is used in producing molded products with markings for distribution management and quality management, a marking device, in addition to the gas-exhausting apparatus (E), needs to be positioned to face the cavity (C). Accordingly, irregularity is caused on the surface of the molded products by the marking device as well as by the upper surface of the gas-exhausting apparatus (E). Such irregularity is not preferable in terms of the outer appearance of the products.
In order to minimize the irregularity on the product surface, the gas-exhausting apparatus (E) and the marking device must be carefully attached to the molding device, which requires a lot of labor in setting up the molding device for manufacturing molded products.